would round the 39 upwards to 40. For example, let’s divide 231 by 39. We set the problem out like
this:
We divide both numbers by 10, so 231 becomes 23.1 and 40 becomes 4. Four won’t divide into 2, so
we divide 4 into 23. Four divides 5 times into 23 with 3 remainder (4 × 5 = 20). We carry the 3
remainder to the next digit, 1, making 31. Our work looks like this:
We correct our remainder for 39 instead of 40 by adding 5 times the 1, which we added to make 40.
5 × 1 = 5
31 + 5 = 36
Our answer is 5 with 36 remainder.Remember, these are only estimates. In the following case we have a situation where the estimate is
not correct, because 39 is less than 40. Let’s say we want to divide 319 by 39. Again, we round off to
- Our calculation would look like this:
We divide both numbers by 10.Four divides into 31 seven times, with 3 remainder. We write the 7 below the 1 in 31 and carry the 3
remainder to the next digit, 9, making 39.
We multiply our answer, 7, by the + 1 to get 7. We add 7 to 39, giving an answer of 46, which is our
remainder. We can’t have a remainder greater than our divisor, so, in this case, we have to raise the last
digit of our answer by 1, to 8.